Design and preparation of metal-based carbon nanosheets for C–O bond cleavage in the absence of external H2

Article abstract of DOI:10.1002/jccs.202100150

A facile yet sustainable approach for the production of Ni₃S₂-doped ultrathin carbon nanosheets in one-pot with very thin thickness of 30 nm was reported. Reaction of nickel nitrate hexahydrate, sodium lignosulfonate with boric acid could produce ultrathin carbon nanosheets. In comparison with the conventional method for the synthesis of Ni₃S₂-doped ultrathin carbon nanosheets, this reaction did not require second vulcanization step. Sodium lignosulfonate was used as carbon and sulfur source. Boric acid was used as 2D template and it could also be readily recycled for repeated use by simply evaporative crystallization. Ni₃S₂-doped ultrathin carbon nanosheets was expected to be an excellent catalyst for C–O bond cleavage under 260°C through catalytic transfer hydrogenation process. In addition, the optimal catalyst could also be recovered in the end.

Full text of DOI:10.1002/jccs.202100150

Received: 22 April 2021
Revised: 5 June 2021
Accepted: 7 June 2021
DOI: 10.1002/jccs.202100150
C O M M U N I C A T I O N
Design and preparation of metal-based carbon nanosheets
for C–O bond cleavage in the absence of external H2
Changzhou Chen1 | Minghao Zhou2 | Jianchun Jiang1
1Institute of Chemical Industry of Forest
Abstract
Products, Chinese Academy of Forestry;
Key Lab. of Biomass Energy and Material,
Jiangsu Province; National Engineering
Lab. for Biomass Chemical Utilization;
Key and Open Lab. on Forest Chemical
Engineering, SFA, Nanjing, China
2School of Chemistry and Chemical
Engineering, Yangzhou University,
Yangzhou 225002, China
A facile yet sustainable approach for the production of Ni3S2-doped ultrathin
carbon nanosheets in one-pot with very thin thickness of 30 nm was reported.
Reaction of nickel nitrate hexahydrate, sodium lignosulfonate with boric acid
could produce ultrathin carbon nanosheets. In comparison with the conven-
tional method for the synthesis of Ni3S2-doped ultrathin carbon nanosheets,
this reaction did not require second vulcanization step. Sodium lignosulfonate
was used as carbon and sulfur source. Boric acid was used as 2D template and
it could also be readily recycled for repeated use by simply evaporative crystal-
lization. Ni3S2-doped ultrathin carbon nanosheets was expected to be an excel-
lent catalyst for C–O bond cleavage under 260ꢀC through catalytic transfer
hydrogenation process. In addition, the optimal catalyst could also be recov-
ered in the end.
Correspondence
Minghao Zhou, School of Chemistry and
Chemical Engineering, Yangzhou
University, Yangzhou 225002, China.
Email: zhouminghao@yzu.edu.cn
Funding information
National Natural Science Foundation of
China, Grant/Award Numbers: 31700645,
31890773
K E Y W O R D S
catalytic transfer hydrogenation, C–O bond cleavage, Ni3S2-doped carbon nanosheets,
ultrathin
1 | INTRODUCTION
of supported noble metals, such as Pd,[3] Pt,[4] Ru,[5]
and Rh[6] have been reported to be effective in the cat-
As well-known, 2D carbon nanostructures have shown
great potential in vast fields such as catalysis, biotechnol-
ogy, energy storage, and conversion due to the unique
electronic properties in confined dimension of nanophase
sp2-hybridized carbon. Nickel sulfide (NiS), a p-type
semicond
uctor, has also attracted increasing attention due to
its low-cost, good electrical properties, and another
unique property such as highly photocatalytic effect
toward the polysulfide reaction.[1] All of these features
make NiS environmentally benign materials that may be
alternatives of many conventionally used reagents,
including catalysts.[2]
alytic system. For example, Galkin et al. reported that
Pd/C could catalyze transfer hydrogenolysis of β-O-4
model compound in lignin employing formic acid as
hydrogen-donor for the generation of acetophenone
and phenol derivates.[7] Paone et al. reported the trans-
fer hydrogenolysis of α-O-4 model compound in lignin
conducted on Pd/Fe3O4 under 240ꢀC.[8] Wu et al.
found that Ru/C could efficiently catalyze the cleavage
of the 4-O-5 aromatic ether bond in a variety of lignin-
derived compounds through the transfer hydro-
genolytic pathway using isopropanol as the hydrogen-
donor solvent.[9] However, the usage of noble metal-
based catalysts could significantly raise production
costs. Moreover, sodium lignosulfonate, which came
from the residue of pulp and boric acid could also be
readily recycled for repeated use by simply evaporative
crystallization from the waste liquid. Herein, we
In the past decades, tremendous efforts have been
devoted to the catalytic transfer hydrogenation of lig-
nin model compounds (β-O-4 ether bond) for the gen-
eration of value-added aromatics. In general, a variety
J Chin Chem Soc. 2021;68:1181–1185.
http://www.jccs.wiley-vch.de
© 2021 The Chemical Society Located in Taipei & Wiley-VCH GmbH
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CHEN ET AL.
FIGURE 1 Images and
spectrum: (a) photograph of the as-
prepared material; (b) SEM images of
carbon nanosheets; (c) SEM images
of Ni3S2-doped carbon nanosheets;
(d) EDX spectrum of Ni3S2-doped
carbon nanosheets. (e–g) element
mapping of Ni3S2-CSs-0.4
reported a new alternative method for catalytic trans-
fer hydrogenation of lignin model compounds to the
corresponding aromatics over an eco-friendly and
environmentally friendly catalyst Ni3S2-doped carbon
nanosheets.
2.2 | General procedure for the reactions
About 100 mg of phenethoxybenzene and 20 mg of
Ni3S2-doped carbon nanosheets in 10 ml of isopropanol
were added into a 25 ml stainless Parr autoclave. The
reaction system was then heated at 260ꢀC for 4 hr with
stirring at 600 rpm. The reaction mixture was followed
analyzed by the gas chromatograph/mass spectrometer
employing n-dodecane as an internal standard. Ni3S2-
doped carbon nanosheets could also be recycled by
centrifugal separation in recovery and the solvent was
evaporated by rotary evaporator.
2 | EXPERIMENTAL DETAILS
2.1 | General procedures for the
preparation of Ni3S2-doped carbon
nanosheets
Boric acid (8 g) was dissolved into deionized water at
80ꢀC, followed by adding the sodium lignosulfonate
(1 g) under magnetic stirring. Then, nickel nitrate
hexahydrate of different quality (0, 0.2, 0.4, 0.6, 0.8 g)
was added in the mixture. The mixture solution was
kept at 80ꢀC under stirring until the water was evapo-
rated. The dark yellow resultant composite was then
annealed at desired temperatures (700ꢀC) for 2 hr at a
ramp rate of 5ꢀC/min in N2 flow, yielding a black pow-
dery product. The black powdery product was then
washed with deionized water and ethanol for three
times. In the end, the obtained black powdery product
was dried at 80ꢀC for 12 hr to yield desired Ni3S2-
doped carbon nanosheets.
2.3 | Instrumental information
Powder X-ray diffraction patterns of Ni3S2-doped car-
bon nanosheets were performed on a Bruker D8
Advance X-ray powder diffractometer using Ni-filtered
Cu Kα radiation (λ = 1.5406 Å) with a scan speed of 2ꢀ
minÀ1 and a scan range of 5–80ꢀ at 30 kV and 15 mA.
Scanning electron microscopy was investigated using a
TESCAN-VEGA3 instrument. X-ray photoelectron
spectroscopy was performed to test the element states
of metal Ni using thermo Fisher ESCALAB-250 X-ray
photoelectron spectroscopy with Al-Kα as the photon
source.

CHEN ET AL.
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FIGURE 2 Images and spectrum: (a) XRD pattern of Ni3S2-doped carbon nanosheets; (b–d) XPS spectra of Ni3S2-CSs-0.4
3 | RESULTS AND DISCUSSION
crystallinity. It probably resulted from a low content
amount of Ni. The XRD patterns of the Ni3S2-CSs-0.4,
Ni3S2-CSs-0.6, and Ni3S2-CSs-0.8 showed diffraction
peaks with the 2θ values of 31.104ꢀ, 38.271ꢀ, 44.330ꢀ,
49.733ꢀ, and 55.161ꢀ, which were corresponding to the
(110), (021), (202), (113), and (122) planes of Ni3S2
(Heazlewoodite, JCPDS No. 44-1418, a = b = 5.745 Å,
c = 7.135 Å).[10] Figure 2b–d depicted the XPS spectra of
Ni3S2-CSs-0.4, suggesting the presence of C, S, and Ni in
the as-prepared material. In C1s spectra (Figure 2b), it
showed three main peaks at 284.70, 286.05, and
288.05 eV corresponding to C-C, C-S, and C=O.[11] In
S2p spectra (Figure 2c), the peak at 162.13 and 163.80 eV
was attributed to Ni-S in Ni3S2-CSs-0.4. The S2p peaks at
165.20 and 167.25 eV shown in Figure 2c were attributed
to C-S in Ni3S2-CSs-0.4. The main peaks of XPS spectra of
Ni 2p (Figure 2d) located around 855.10 and 857.56 eV
were corresponding to Ni 2p3/2, whereas the peaks at
873.53 and 874.61 eV were corresponding to Ni 2p1/2.
The as-prepared Ni3S2-doped carbon nanosheets was in
black color and then it could be picked up by magnet
(Figure 1a). In comparison, no Ni introduced in the carbon
nanosheets was prepared, and the SEM image of 2D
nanosheets with smooth surface was obtained in Figure 1b.
The accurate thickness of 2D Ni3S2-doped carbon
nanosheets was ultrathin, which could be seen in Figure 1c.
With the increase in loading amount of nickel nitrate hexa-
hydrate, Ni3S2-doped carbon nanosheets with 0.4 g nickel
nitrate hexahydrate could be clearly seen in Figure 1c. Ni3S2
particle displayed outside the activated carbon uniformly.
The elemental mapping results (Figure 1e–g) of the Ni3S2-
doped carbon nanosheets suggested that Ni and S were well
dispersed in the carbon nanosheets with distinct morphol-
ogy of the nanoparticles.
The low peak intensities of the XRD patterns of
Ni3S2-doped carbon nanosheets (Figure 2a) showed weak

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FIGURE 3 (a) Catalyst screening
of the C–O bond cleavage;
(b) possible pathway of
(a)
O
O
OH
Ni3S2-CSs
iPrOH, 2 MPa N2
phenethoxybenzene transformation;
(c) cleavage of different lignin model
compounds over Ni3S2-CSs-0.4
catalyst
1
Entry
1
2
3
4
Products yield (2,3,4)
Catalyst
Ni3S2-CSs-0
Ni3S2-CSs-0.2
Ni3S2-CSs-0.4
0, 0, 0
2
25%, 60%, 56%
3
4
2%, 92%, 90%
Ni3S2-CSs-0.6
Ni3S2-CSs-0.8
Ni/CNT
3%, 92%, 91%
2%, 93%, 90%
31%, 70%, 69%
5
6
(b)
(c)
O
O
OH
Cat.
isopropanol
+H
O
O
OH
OH
O
71%
88%
72%
87%
O
The other peaks were satellite peaks.[12–14] The SEM,
XRD, and XPS results demonstrated the successful forma-
tion of Ni3S2-doped carbon nanosheet.
phenethoxybenzene to corresponding aromatics, iso-
propanol was served as a good H-donner solvent, which
could provide a large amount of active hydrogen to pro-
mote the cleavage of the C–O bond. Additionally, a small
amount of acetone was observed in the reaction system.
In compression, Ni/CNT was used under the optimal
reaction condition, moderate conversion was achieved.[15]
Thus, Ni3S2-CSs-0.2 was the optimal catalyst (Figure 3a,
entry 6). The possible pathway of phenethoxybenzene
transformation could be seen in Figure 3b. Different
lignin model compounds were then explored over Ni3S2-
CSs-0.4 catalyst. It was found that good yields of
aromatics were obtained as shown in Figure 3c.
Ni3S2 compounds were employed as catalyst of reduc-
tive reactions for the catalytic activity of nickel. There-
fore, we tried to apply Ni3S2-doped carbon nanosheet as
catalyst in reductive reactions such as hydrogenolysis of
lignin model compounds. The blank reaction of cleavage
of C–O bond in phenethoxybenzene with isopropanol as
H-donner at 260ꢀC failed to produce ethylbenzene and
phenol (Figure 3a, entry 1). For Ni3S2-CSs-0.2 catalyst,
incomplete conversion, 60% yield of ethylbenzene and
56% yield of phenol were obtained, respectively. More-
over, 25% yield of phenethoxybenzene as the intermedi-
ate compound was also observed (Figure 3a, entry 2). For
the latter three catalysts, total conversion was obtained
and excellent yield of C–O bond cutting products such as
ethylbenzene (> 90% yields over Ni3S2-CSs-0.4, Ni3S2-
CSs-0.6 and Ni3S2-CSs-0.8) and phenol (> 90% yields over
Ni3S2-CSs-0.4, Ni3S2-CSs-0.6 and Ni3S2-CSs-0.8) were
formed as target products. In the transformation of
4 | CONCLUSIONS
In this paper, we designed a sustainable approach for
the production of Ni3S2-doped ultrathin carbon
nanosheets in one-pot with very thin thickness of
30 nm. lignin model compounds (4-O-5, α-O-4, β-O-4)

CHEN ET AL.
1185
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under a mild condition (260ꢀC, 4 hr) employing iso-
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approach will inspire various researches on the hydro-
genation process in the absence of additional hydrogen.
ACKNOWLEDGMENTS
Authors are grateful for the financial support from
National Natural Science Foundation of China
(31890773, 31700645).
CONFLICT OF INTEREST
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The authors declare no conflicts of interest.
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